John G Avildsen, who directed hugely successful underdog fables Rocky and The Karate Kid, has died at age 81.

Avildsen’s son Anthony said his father died on Friday (local time) in Los Angeles from pancreatic cancer.

“He was a pretty extraordinary man in my estimation. He was super talented and very driven and very stubborn and that was to his detriment but also often to his benefit,” Anthony Avildsen said.

Avildsen took a chance on Rocky, written by and starring the then-unknown Sylvester Stallone as a struggling boxer.

Stallone paid tribute to the director, saying he owed just about everything to him.

“His directing, his passion, his toughness and his heart — a great heart — is what made Rocky the film it became,” Stallone said.

“He changed my life and I will be forever indebted to him. Nobody could have done it better than my friend John Avildsen. I will miss him.”

Avildsen got involved with Rocky after a friend sent him the Rocky script.

“On page three, this guy [Rocky] is talking to his turtles, and I was hooked,” Avildsen remarked.

“It was a great character study.”

Avildsen agreed to direct Rocky even though he knew nothing about boxing.

The 1976 film became a phenomenon that won Oscars for best picture as well as for Avildsen as director.

The Karate Kid was another surprise hit. The 1984 film told the story of a teen who learns about self-confidence through the study of karate.

Five sequels followed, but Avildsen turned them down, until the fourth, Rocky V, in 1990. He said he considered it a good script and liked that Rocky would die. During the shooting the producers decided Rocky had to live.

Avildsen had come up the hard way in films. He started with a long apprenticeship as assistant director, then moved up to production manager, cinematographer and editor.

Underdogs winning creates ‘good drama’

Avildsen outlined his view of filmmaking during an interview in 1992.

“I don’t see my films as following any strict formula — even if many of them do have a similar theme,” he said.

He directed a few small films and then broke through with 1970s Joe, in which Peter Boyle portrayed a hardhat bigot at odds with the emerging hippie youth culture.

Avildsen directed other major stars, including: Burt Reynolds in WW and the Dixie Dancekings (1975); George C Scott and Marlon Brando in The Formula (1980); Dan Aykroyd and John Belushi in Neighbors (1981); and Morgan Freeman in Lean on Me (1989).

He had been hired to direct Saturday Night Fever after his success with Rocky, but was let go amid differences over his desire to make the story more upbeat than the producers had in mind.

Avildsen is survived by his sons Jonathan, Ashley and Anthony, and daughter Bridget.